Field of the Invention
The invention relates to a cylinder device and a vehicle brake system.
Description of the Related Arts
A cylinder device is conventionally known, as shown in, for example, Japanese Patent Application Publication No. 2009-126355 (see FIG. 6), which is used in a vehicle brake system that generates brake hydraulic pressure in response to control input on a brake operating element.
This cylinder device includes a front piston, a rear piston, and a regulation mechanism therebetween. The regulation mechanism includes a retainer that is fixed to a rear end of the front piston, a bolt that has its head engaged with a rear end of the retainer and is screwed into a front end of the rear piston, a spring seat member that is fixed to the front end of the rear piston by the screwed bolt, and a spring compressively arranged between the retainer and the spring seat member.
Arranged on the outer edge of the spring seat member are a spring reception part extending forward toward the spring and a cup seal holding part extending backward toward a cup seal.